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Poly bushings and speed determinate vibration

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  • Poly bushings and speed determinate vibration

    From day one my car has had a vibration in the front between 51-54 mph. The tires have been rotated several times and the vibration does not go away.

    I have rocked the wheel at both 12 and 6 o'clock and 9 and 3 o'clock and there is the slightest wiggle. However, tightening the castle nut seems to make the wheel too tight with too much drag. No idea the brand of bearings in there.

    Should I suspect worn rubber bushings? They are about ten years old (I've had the car for 4 years.)

    My main question about poly bushings relate to ride harshness. I have BPNW 1" HD lowering springs, which definitely give a firmer ride. I don't want this thing to rattle my teeth even on smooth roads. So, do different manufacturers poly bushing have a different "harshness" to them?

    What about squeaking? How do you prevent it?
    1972 Sapphire TR6 #CC84,something

    1959 Red TR3 (Wife's)

  • #2
    How are your inner tie rods? Might be worth putting the car upon stands, popping the ends out and checking if they’re super loose. You can also have some amount of play in the trunnion hardware. The A-Arms could be slightly loose. That’s something else I’ll be addressing on my 6

    Comment


    • #3
      What about your steering rack clamps/bushings? Do you have stock clamps with rubber bushings or solid alloy clamps? The alloy clamps definitely transmit more vibration thru the steering. And likely more wear.
      Keith, Huntsville AL, 1971 CC66559
      10.0:1 CR gasflowed head | Weber DCOEs | CP "150hp" Cam | Distibutor by Advanced | Lightened flywheel | Phoenix SS Exhaust System | HVDA 5-Speed | Good Parts suspension and anti-roll bars | Konig Rewinds | Boyd 15 gal tank | Miata Seats and Mr Mikes covers | Carl Visser dash | Mohair hood

      Comment


      • #4
        But as I said last week, come by and we’ll try my set of Konigs on your car before you start tearing anything apart. Original Steel wheels are notorious for having excessive runout

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        • #5
          Originally posted by skootch13 View Post
          I have rocked the wheel at both 12 and 6 o'clock and 9 and 3 o'clock and there is the slightest wiggle. However, tightening the castle nut seems to make the wheel too tight with too much drag. No idea the brand of bearings in there.
          There shouldn't be any lateral movement of the wheel when off the ground.

          Walt
          CC80954U '72 TR6 original condition/sold 16.500.
          poolboy rebuilt the Z-S Carbs. Philstr6 rebuilt both rear hubs.

          Comment


          • #6
            Apart from bent wheels ( and I thought the '70+ TR6 wheels were pretty immune to this, while '69 and TR4/250 wheels especially prone thereto ) or improperly balanced wheels I don't think the faults mentioned above will be the vibration culprit.

            As for poly bushings, I have these in one car ( concourse, 6K miles in 9 years ) and rubber in the driver ( 5K+ miles/year ). I'll never use poly again, as I'm 100% satisfied with the behavior of the steering and suspension with rubber. All stock springs, KONI shocks in front and everything snug and set up properly w/r/t camber, castor and alignment. Both have their original, 1968 steering rack bushings properly compressed. Tires are vintage Michelin 185s in both cases ( XVS and XWX ).

            Poly is harder and squeaks eventually. The worst offender is the ARB bushings. Any advantage in handling over the rubber can be easily compensated with skill , and the rest of the time the superior ride quality vindicates the choice [ stock rubber ] resoundingly.

            Tom

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            • #7
              I'm going to be investigating a similar problem in the next few weeks myself. My vibration is between 70-75 MPH.
              • Problem has developed over the past couple years
              • Aluminum steering rack mounts installed 5 years ago
              • Rubber bushings installed 5 years ago
              • Koenig Wheels with recently balanced but 7 year old tires.
              • Bearings are original but recently tightened by a pro
              • Things I wonder about​​​​​​​
                • Tires are recently balanced but...7 years old
                • Trunnions are original
                • Steering rack has never been touched
                • Ball joints are 20 years old
                • Tie-rod ends are 20 years old
              73 TR6
              Libertyville, IL
              My TR6

              Comment


              • #8
                Many wheel balancing machines locate the wheel by its center hole. However to get proper balance, a stamped steel wheel should be balanced on a machine that is "lug-centric". When the wheel is on the car, the lugs locate it, not the center hole. Particularly with stamped steel, there can be some non-concentricity between the lug circle and the center of the wheel. This is less of an issue on alloy wheels.
                1976 TR-6 BRG - CF57239U
                Carbs by Poolboy
                Rear Camber Kit, Rear Hubs by Goodparts
                Gear Reduction Starter by TSI
                Distributor by British Vacuum

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                • #9
                  Oh and, BTW, I had a vibration at 60-75 for years when I had the original steel wheels. Replaced the steelies with Koenigs and things were smooth as silk until a couple years back. Definitely go with Todd's suggestion of trying out the Koenigs first.
                  73 TR6
                  Libertyville, IL
                  My TR6

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                  • #10
                    Wheels can be checked for runout without fancy equipment. Just place blocks next to the suspect wheel and spin it with a pointer atop the stack ( screwdriver is fine ) touching the rim face about 1/4" in from the outside diameter. The naked eye will give an adequate indication. Tolerance per Uncle Bentley is 0.040" or 2/3 of a 16th".

                    On TR4/250 wheels the center disc can be easily bent by wrenching the poor things on a tire dismounting machine. TR6 wheels perhaps likewise. The bulged portion just outside of the flat zone is virtually impossible to bend, so the disc can be beaten back beyond it with a sledgehammer for an outwardly convex shape, which becomes perfectly flat again once bolted to the hub. If a straightedge across the mounting surface reveals this fault then it's time to get the sledge out.

                    Tom ( running with Panasports since way back in the 1900s )
                    Last edited by ima68tr; 10-03-2018, 11:33 AM.

                    Comment


                    • #11
                      Originally posted by ima68tr View Post
                      Apart from bent wheels ( and I thought the '70+ TR6 wheels were pretty immune to this, while '69 and TR4/250 wheels especially prone thereto ) or improperly balanced wheels I don't think the faults mentioned above will be the vibration culprit.

                      As for poly bushings, I have these in one car ( concourse, 6K miles in 9 years ) and rubber in the driver ( 5K+ miles/year ). I'll never use poly again, as I'm 100% satisfied with the behavior of the steering and suspension with rubber. All stock springs, KONI shocks in front and everything snug and set up properly w/r/t camber, castor and alignment. Both have their original, 1968 steering rack bushings properly compressed. Tires are vintage Michelin 185s in both cases ( XVS and XWX ).

                      Poly is harder and squeaks eventually. The worst offender is the ARB bushings. Any advantage in handling over the rubber can be easily compensated with skill , and the rest of the time the superior ride quality vindicates the choice [ stock rubber ] resoundingly.

                      Tom
                      70-76 wheels are NOT immune. I’ve checked many and many that checked have unacceptable run out

                      As far as rubber vs poly, I’m sure rubber is just fine providing it’s in proper shape. I’m of the opinion that rubber fails a lot faster than poly. So in your case, the poly bushes may never need replacing (in your lifetime) based on your mileage/year. The rubber bushes would simply perish over time.

                      I think if you’re going to replace bushings especially in the trailing arms, the harder (nylatron) bushes are the way to go. I’ve experienced poly bushes Ovalling resulting from my driving habits.

                      YMMV

                      Todd

                      Comment


                      • #12
                        Originally posted by tr250 View Post
                        But as I said last week, come by and we’ll try my set of Konigs on your car before you start tearing anything apart. Original Steel wheels are notorious for having excessive runout
                        This is a good idea.

                        Vibe in that speed range is typically some type of balance issue, in my experience.
                        '74 TR6 CF13007U aka "Mr. T"
                        Custom Blue (Delft-Like) and New Tan (Formerly Mallard and New Tan)
                        Points, Ballast Bypassed, Bosch Blue Coil, Moss Cobalt Wires, Champion RN12YC plugs.
                        Peaks and tweaks, but the spirit of Original
                        Redlines always.
                        My wife is the Driver, I'm just the Mechanic....

                        Comment


                        • #13
                          I too had speed related vibration issues and it was a tire out of round. Parking during the off season after 10 years likely produced a weak spot. The tires didn't have much wear, but all those winters parked added up. My car is stored out of state during the off season so I can’t roll it back and forth.

                          Since then I’ve increased tire pressure during winter storage..
                          1974 TR-6 Logic Overdrive

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                          • #14
                            Hey Mike, that's interesting and makes me think the first place to look in my case would be the tires. 7 years old and my car is in storage 4 months of the year.
                            73 TR6
                            Libertyville, IL
                            My TR6

                            Comment


                            • #15
                              A vibration at some very specific speed says that something is out of balance and you’ve hit a resonance that causes the vibration. Out of balance drive shafts are a typical cause of this type specific speed vibration. I would look to get the tires properly balanced.
                              Loose bits in the suspension will give vibrations at any speed. And will result in odd wear patterns on the tires, scallops, or uneven bumps, things like that.
                              I prefer the poly bushings for a bit more stiffness and longevity. Installed along with a generous amount of silicone grease and 4 years on, still no squeaks. And , yes, different manufacturers poly will give different results. Poly can be made with a very wide range of properties.
                              The front wheels will have a bit of lateral movement at 3-9 and 6-12. The bearings will drag too much if they are preloaded enough to prevent any movement.
                              ‘70 TR-6

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                              Poly bushings and speed determinate vibration

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